Maybe Last Crusade could be described as tongue in cheek. And Crystal Skull is basically a parody, lol. But Raiders is a really earnest, sincere adventure flick, which is why it's such an enduring classic. And I agree that it's tonally about what Guardians should aim for.

As I said, much of the action/humor/violence in Raiders has been (rightly) described as tongue-in-cheek. Almost all of the often brutal violence has a humorous punchline - the scene in Marion's bar has like ten such incidents.

You must have a narrow or different definition of tongue-in-cheek than the one commonly used, which is fine. Leave it at that.